Secondary battery, battery pack, electronic device, electric tool, electric aircraft, and electric vehicle

ABSTRACT

Provided is a secondary battery including: an electrode wound body that has a positive electrode and a negative electrode stacked with a separator interposed therebetween and has a wound structure; and a positive electrode current collecting plate and a negative electrode current collecting plate, accommodated in an exterior can, where the positive electrode includes a first covered part covered with a positive electrode active material layer and a positive electrode active material non-covered part on a positive electrode foil, and the negative electrode includes a second covered part covered with a negative electrode active material layer and a negative electrode active material non-covered part on a negative electrode foil.

ROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of PCT patent application no.PCT/JP2020/027426, filed on Jul. 15, 2020, which claims priority toJapanese patent application no. JP2019-139812 filed on Jul. 30, 2019,the entire contents of which are being incorporated herein by reference.

BACKGROUND

The present disclosure generally relates to a secondary battery, abattery pack, an electronic device, an electric tool, an electricaircraft, and an electric vehicle.

Lithium ion batteries have been widely used in automobiles, machines,and the like, and high-power batteries have been required. As one ofmethods for producing this high power, high-rate discharge has beenproposed. The high-rate discharge is discharge in which a relativelylarge current flows, and in such a case, the internal resistance of thebattery has a problematic magnitude. Examples of the internal resistanceof the battery include contact resistances among a positive electrodefoil, a negative electrode foil, and a current collecting plate forcurrent extraction.

SUMMARY

The present disclosure generally relates to a secondary battery, abattery pack, an electronic device, an electric tool, an electricaircraft, and an electric vehicle.

The conventional battery technology, for example, has the eight bendingsupport grooves formed radially from the outer edge of the spiralelectrode body to the central axis, and the welded region between thecurrent collector exposed part and the current collecting plate is thusreduced in the vicinity of the central axis of the spiral electrodebody, thereby causing the problem of failing to lead to a reduction ininternal resistance.

Accordingly, an object of the present disclosure is to provide a batteryincluding a groove that has a shape capable of reducing the internalresistance of the battery.

For solving the above-described problems, the present disclosureprovides a secondary battery according to an embodiment including: anelectrode wound body that has a positive electrode and a negativeelectrode stacked with a separator interposed therebetween and has awound structure; and a positive electrode current collecting plate and anegative electrode current collecting plate, accommodated in an exteriorcan,

where the positive electrode includes a first covered part covered witha positive electrode active material layer and a positive electrodeactive material non-covered part on a positive electrode foil, and

the negative electrode includes a second covered part covered with anegative electrode active material layer and a negative electrode activematerial non-covered part on a negative electrode foil,

the positive electrode active material non-covered part is joined to thepositive electrode current collecting plate at a first end of theelectrode wound body, and

the negative electrode active material non-covered part is joined to thenegative electrode current collecting plate at a second end of theelectrode wound body,

one or both of the positive electrode active material non-covered partand the negative electrode active material non-covered part have a flatsurface formed by bending toward the central axis of the wound structureand overlapping each other,

the flat surface has a first groove passing through the central axis anda second groove not passing through the central axis, and

a part of the flat surface without any groove passing through thecentral axis or groove not passing through the central axis is bonded toat least one of the positive electrode current collecting plate or thenegative electrode current collecting plate.

Further, the present disclosure provides a battery pack according to anembodiment including:

the secondary battery described above;

a controller configured to control the secondary battery; and

an exterior body that encloses the secondary battery.

The present disclosure provides an electronic device according to anembodiment including the secondary battery or the battery pack asdescribed herein.

The present disclosure provides an electric tool according to anembodiment including the battery pack as described herein. The electrictool is configured to use the battery pack as a power supply.

The present disclosure provides an electric aircraft according to anembodiment including:

the battery pack described above;

a plurality of rotor blades;

a motor that rotates each of the rotor blades;

a support shaft that supports each of the rotor blades and the motor;

a motor controller configured to control rotation of the motor; and

a power supply line that supplies power to the motor,

where the battery pack is connected to the power supply line.

The present disclosure provides an electric vehicle according to anembodiment including the secondary battery described above, and

including a conversion device that receives power supply from thesecondary battery to convert the power to a driving force for thevehicle, and

a controller configured to perform information processing related tovehicle control, based on information on the battery.

According to at least an embodiment of the present disclosure, theinternal resistance of the battery can be reduced, and a high-powerbattery can be achieved.

It should be understood that the effects described in the presentspecification are only examples, which do not impose limitations, andadditional effects may be further provided.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic sectional view of a battery according to anembodiment of the present disclosure.

FIG. 2 is a diagram illustrating an example of a relationship among apositive electrode, a negative electrode, and a separator disposed in anelectrode wound body according to an embodiment of the presentdisclosure.

FIG. 3A is a plan view of a positive electrode current collecting plateaccording to an embodiment of the present disclosure, and FIG. 3B is aplan view of a negative electrode current collecting plate according toan embodiment of the present disclosure.

FIG. 4A to 4F are diagrams illustrating a process for assembling abattery according to an embodiment of the present disclosure.

FIGS. 5A and 5B are diagrams illustrating Example 1 according to anembodiment of the present disclosure.

FIGS. 6A and 6B are diagrams illustrating Example 2 according to anembodiment of the present disclosure.

FIGS. 7A and 7B are diagrams illustrating Comparative Example 1.

FIGS. 8A and 8B are diagrams illustrating Comparative Example 2.

FIGS. 9A and 9B are diagrams illustrating Comparative Example 3.

FIGS. 10A and 10B are diagrams illustrating Comparative Example 4.

FIGS. 11A and 11B are diagrams illustrating Comparative Example 5.

FIG. 12A to 12D are diagrams illustrating examples of grooves accordingto an embodiment of the present disclosure.

FIG. 13 is a connection diagram for use in description of a battery packas an application example according to an embodiment of the presentdisclosure.

FIG. 14 is a connection diagram for use in description of an electrictool as an application example according to an embodiment of the presentdisclosure.

FIG. 15 is a connection diagram for use in description of an unmannedaircraft as an application example according to an embodiment of thepresent disclosure.

FIG. 16 is a connection diagram for use in description of an electricvehicle as an application example according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION

As described herein, the present disclosure will be described based onexamples with reference to the drawings, but the present disclosure isnot to be considered limited to the examples, and various numericalvalues and materials in the examples are considered by way of example.

In the embodiment of the present disclosure, a cylindrical lithium ionbattery will be described as an example of the secondary battery.Obviously, any battery other than the lithium ion battery or a batterythat has any shape other than the cylindrical shape may be used. Thepresent disclosure may be applied to a Li—S battery (lithium-sulfursecondary battery).

First, the overall configuration of the lithium ion battery will bedescribed. FIG. 1 is a schematic sectional view of a lithium ion battery1. The lithium ion battery 1 is, for example, a cylindrical lithium ionbattery 1 that has an electrode wound body 20 is housed inside anexterior can 11 as shown in FIG. 1.

Specifically, the lithium ion battery 1 includes, for example, a pair ofinsulating plates 12 and 13 and an electrode wound body 20 inside thecylindrical exterior can 11. The lithium ion battery 1 may further,however, include, for example, any one of, or two or more of a positivetemperature coefficient (PTC) element, a reinforcing member, and thelike inside the exterior can 11.

The exterior can 11 is a member that mainly houses the electrode woundbody 20. The exterior can 11 is, for example, a cylindrical containerwith one end thereof opened and the other end thereof closed. Morespecifically, the exterior can 11 has an opened end (open end 11N). Theexterior can 11 contains, for example, any one of, or two or more ofmetal materials such as iron, aluminum, and alloys thereof. The surfaceof the exterior can 11 may be, however, plated with, for example, anyone of, or two or more of metal materials such as nickel.

Each of the insulating plates 12 and 13 is, for example, a dish-shapedplate that has a surface perpendicular to the winding axis of theelectrode wound body 20, that is, a surface perpendicular to the Z axisin FIG. 1. In addition, the insulating plates 12 and 13 are disposed soas to sandwich the electrode wound body 20 therebetween, for example.

The open end 11N of the exterior can 11 has, for example, a batterycover 14 and a safety valve mechanism 30 are crimped with a gasket 15.The battery cover 14 serves as a “cover member” according to anembodiment of the present disclosure, and the gasket 15 serves as a“sealing member” according to an embodiment of the present disclosure.Thus, with the electrode wound body 20 and the like housed inside theexterior can 11, the exterior can 11 is sealed. Accordingly, the openend 11N of the exterior can 11 has a structure (crimped structure 11R)formed by the battery cover 14 and the safety valve mechanism 30 crimpedwith the gasket 15. More specifically, a bent part 11P is a so-calledcrimp part, and the crimped structure 11R is a so-called crimpstructure.

The battery cover 14 is a member that closes the open end 11N of theexterior can 11 mainly with the electrode wound body 20 and the likehoused inside the exterior can 11. The battery cover 14 contains, forexample, the same material as the material that forms the exterior can11. The central region of the battery cover 14 protrudes in the +Zdirection, for example. Thus, the region (peripheral region) of thebattery cover 14 other than the central region has contact with, forexample, the safety valve mechanism 30.

The gasket 15 is a member mainly interposed between the exterior can 11(bent part 11P) and the battery cover 14 to seal the gap between thebent part 11P and the battery cover 14. For example, asphalt or the likemay be, however, applied to the surface of the gasket 15.

The gasket 15 contains, for example, any one of, or two or more ofinsulating materials. The types of the insulating materials are notparticularly limited, and may be, for example, a polymer material suchas a polybutylene terephthalate (PBT) and a polypropylene (PP). Inparticular, the insulating material is preferably a polybutyleneterephthalate. This is because the gap between the bent part 11P and thebattery cover 14 is sufficiently sealed while the exterior can 11 andthe battery cover 14 are electrically separated from each other.

The safety valve mechanism 30 mainly releases the sealed state of theexterior can 11 to release the pressure (internal pressure) inside theexterior can 11, if necessary, when the internal pressure is increased.The cause of the increase in the internal pressure of exterior can 11is, for example, a gas generated due to a decomposition reaction of anelectrolytic solution during charging or discharging.

For the cylindrical lithium ion battery, a band-shaped positiveelectrode 21 and a band-shaped negative electrode 22 are spirally woundwith a separator 23 interposed therebetween, impregnated with anelectrolytic solution, and housed in the exterior can 11. The positiveelectrode 21 is obtained by forming a positive electrode active materiallayer 21B on one or both surfaces of a positive electrode foil 21A, andthe material of the positive electrode foil 21A is, for example, a metalfoil made of aluminum or an aluminum alloy. The negative electrode 22 isobtained by forming a negative electrode active material layer 22B onone or both surfaces of a negative electrode foil 22A, and the materialof the negative electrode foil 22A is, for example, a metal foil made ofnickel, a nickel alloy, copper, or a copper alloy. The separator 23 is aporous and insulating film, which enables transfer of substances such asions and an electrolytic solution while electrically insulating thepositive electrode 21 and the negative electrode 22.

The positive electrode active material layer 21B and the negativeelectrode active material layer 22B respectively cover most of thepositive electrode foil 21A and the negative electrode foil 22A, butintentionally, neither of the layers covers one end periphery in theshort axis direction of the band. Hereinafter, the part covered with noactive material layer 21B or 22B is appropriately referred to as anactive material non-covered part. In the cylindrical battery, theelectrode wound body 20 is wound in such a manner that an activematerial non-covered part 21C of the positive electrode and an activematerial non-covered part 22C of the negative electrode are overlappedwith each other with the separator 23 interposed therebetween so as toface in opposite directions.

FIG. 2 shows an example of a structure with the positive electrode 21,the negative electrode 22, and the separator 23 stacked before winding.The active material non-covered part 21C (the upper hatched part in FIG.2) of the positive electrode has a width denoted by A, and the activematerial non-covered part 22C (the lower hatched part in FIG. 2) of thenegative electrode has a width denoted by B. According to oneembodiment, A>B is preferred, for example, A=7 (mm) and B=4 (mm). A partof the active material non-covered part 21C of the positive electrode,protruded from one end of the separator 23 in the width direction, has alength denoted by C, and a part of the active material non-covered part22C of the negative electrode, protruded from the other end of theseparator 23 in the width direction, has a length denoted by D.According to one embodiment, C>D is preferred, for example, C=4.5 (mm)and D=3 (mm).

The active material non-covered part 21C of the positive electrode ismade of, for example, aluminum, whereas the active material non-coveredpart 22C of the negative electrode is made of, for example, copper, andthus, the active material

non-covered part 21C of the positive electrode is typically softer (hasa lower Young's modulus) than the active material non-covered part 22Cof the negative electrode. Thus, according to one embodiment, A>B andC>D are more preferred, and in this case, when the active materialnon-covered part 21C of the positive electrode and the active materialnon-covered part 22C of the negative electrode are bent at the samepressure simultaneously from both electrode sides, the positiveelectrode 21 and the negative electrode 22 may be similar in the heightof the bent part, measured from the tip of the separator 23. In thiscase, the active material non-covered parts 21C and 22C are bent toappropriately overlap with each other, thus allowing the active materialnon-covered parts 21C and 22C and current collecting plates 24 and 25 tobe easily joined by laser welding. Joining according to one embodimentmeans joining by laser welding, but the joining method is not limited tolaser welding.

For the positive electrode 21, a section of 3 mm in width, including theboundary between the active material non-covered part 21C and the activematerial covered part 21B, is coated with an insulating layer 101 (grayregion part in FIG. 2). Further, the whole region of the active materialnon-covered part 21C of the positive electrode, opposed the activematerial covered part 22B of the negative electrode with the separatorinterposed therebetween, is covered with the insulating layer 101. Theinsulating layer 101 has the effect of reliably preventing any internalshort circuit of the battery 1 if any foreign matter enters between theactive material covered part 22B of the negative electrode and theactive material non-covered part 21C of the positive electrode. Inaddition, the insulating layer 101 has the effect of, when an impact isapplied to the battery 1, absorbing the impact and reliably preventingthe active material non-covered part 21C of the positive electrode frombeing bent or short-circuited with the negative electrode 22.

The central axis of the electrode wound body 20 has a through hole 26formed. The through hole 26 is a hole for insertion of a winding corefor assembling the electrode wound body 20 and an electrode rod forwelding. The electrode wound body 20 is wound in an overlapping mannersuch that the active material non-covered part 21C of the positiveelectrode and the active material non-covered part 22C of the negativeelectrode face in the opposite directions, and thus, the active materialnon-covered part 21C of the positive electrode is gathered at one (end41) of the ends of the electrode wound body, whereas the active materialnon-covered part 22C of the negative electrode is gathered at the other(end 42) of the ends of the electrode wound body 20. For improvingcontact with the current collecting plates 24 and 25 for currentextraction, the active material non-covered parts 21C and 22C are bent,and the ends 41 and 42 have flat surfaces. The bending directions aredirections from the outer edges 27 and 28 of the ends 41 and 42 towardthe through hole 26, and peripheral active material non-covered partsthat are adjacent in the wound state are bent in a manner of overlappingwith each other. In this specification, the “flat surface” includes notonly a perfectly flat surface but also a surface with some unevennessand surface roughness to the extent that the active material non-coveredpart and the current collecting plate can be joined.

When each of the active material non-covered parts 21C and 22C are bentso as to have an overlap, it seems possible for the ends 41 and 42 tohave flat surfaces, but if no processing is performed before bending,wrinkles or voids (voids, spaces) are generated at the ends 41 and 42 atthe time of bending, and the ends 41 and 42 have no flat surfaces. Inthis regard, the “wrinkles” or “voids” are portions where the bentactive material non-covered parts 21C and 22C are biased, therebycausing the ends 41 and 42 to have no flat surfaces. For preventing thegeneration of wrinkles and voids, grooves 43 and 44 (see, for example,FIG. 4B) are formed in advance in radiation directions from the throughhole 26. The central axis of the electrode wound body 20 has the throughhole 26, and the grooves include the groove 43 passing through thecentral axis and the groove 44 not passing through the central axis. Thegroove 43 passing through the central axis is a groove extending fromthe outer edges 27 and 28 of the ends 41 and 42 to the through hole 26in the central axis, and the groove 44 not passing through the centralaxis is a groove in an outer peripheral part without extending to thethrough hole 26. The active material non-covered parts 21C and 22C havenotches at the start of winding the positive electrode 21 and thenegative electrode 22 near the through hole 26. This is for keeping thethrough hole 26 from being closed in the case of bending toward thethrough hole 26. The grooves 43 and 44 remain in the flat surfaces alsoafter bending the active material non-covered parts 21C and 22C, andparts without the grooves 43 and 44 are joined (welded or the like) tothe positive electrode current collecting plate 24 or the negativeelectrode current collecting plate 25. It is to be noted that thegrooves 43 and 44 as well as the flat surfaces may be joined to a partof the current collecting plates 24 and 25.

The detailed configuration of the electrode wound body 20, that is, therespective detailed configuration of the positive electrode 21, negativeelectrode 22, separator 23, and electrolytic solution will be describedlater.

In a common lithium ion battery, for example, a lead for currentextraction is welded to each one of the positive electrode and negativeelectrode, but this is not suitable for high-rate discharge because ofthe high internal resistance of the battery and the temperatureincreased by heat generation of the lithium ion battery in the case ofdischarging. Thus, in the lithium ion battery according to oneembodiment, the internal resistance of the battery is kept low bydisposing the positive electrode current collecting plate 24 and thenegative electrode current collecting plate 25 at the ends 41 and 42,and welding at multiple points to the active material non-covered parts21C and 22C of the positive electrode and negative electrode present atthe ends 41 and 42. The ends 41 and 42 are bent to form flat surfaces,which also contributes to the reduction in resistance.

FIG. 3A and FIG. 3B show examples of the current collecting plates. FIG.3A shows the positive electrode current collecting plate 24, and FIG. 3Bshows the negative electrode current collecting plate 25. The materialof the positive electrode current collecting plate 24 is, for example, ametal plate made of a simple substance of aluminum or an aluminum alloyor a composite thereof, and the material of the negative electrodecurrent collecting plate 25 is, for example, a metal plate made of asimple substance of nickel, a nickel alloy, copper, or a copper alloy ora composite thereof. As shown in FIG. 3A, the positive electrode currentcollecting plate 24 has the shape of a flat fan-shaped part 31 with arectangular band-shaped part 32 attached thereto. The fan-shaped part 31has, near the center thereof, a hole 35 formed, and the hole 35 islocated at a position corresponding to the through hole 26.

A hatched part in FIG. 3A is an insulating part 32A where an insulatingtape is attached to the band-shaped part 32 or an insulating material isapplied thereto, and the part below the hatched part in the drawing is aconnecting part 32B to a sealing plate that also serves as an externalterminal. It is to be noted that in the case of a battery structurewithout any metallic center pin (not shown) in the through hole 26, theband-shaped part 32 has a low probability of coming into contact with asite with a negative electrode potential, and thus, there is no need forthe insulating part 32A. In such a case, the widths of the positiveelectrode 21 and negative electrode 22 can be increased by an amountcorresponding to the thickness of the insulating part 32A to increasethe charge/discharge capacity.

The negative electrode current collecting plate 25 has substantially thesame shape as the positive electrode current collecting plate 24, buthas a different band-shaped part. The band-shaped part 34 of thenegative electrode current collecting plate in FIG. 3B is shorter thanthe band-shaped part 32 of the positive electrode current collectingplate, without any part corresponding to the insulating part 32A. Theband-shaped part 34 has a round protrusion (projection) 37 indicated bya plurality of circles. During resistance welding, current isconcentrated on the protrusion, and the protrusion is melted to weld theband-shaped part 34 to the bottom of the exterior can 11. Similarly tothe positive electrode current collecting plate 24, the negativeelectrode current collecting plate 25 has a hole 36 near the center of afan-shaped part 33, and the hole 36 is located at a positioncorresponding to the through hole 26. The fan-shaped part 31 of thepositive electrode current collecting plate 24 and the fan-shaped part33 of the negative electrode current collecting plate 25 have a fanshape, and thus cover a part of the ends 41 and 42. The reason that thewhole is not covered to allow an electrolytic solution to smoothlypermeate the electrode wound body in the assembly of the battery, or tomake it easier for the gas generated when the battery reaches anabnormally high-temperature state or overcharge state to be released tothe outside of the battery.

The positive electrode active material layer 21B includes, as a positiveelectrode active material, any one of, or two or more of positiveelectrode materials capable of occluding and releasing lithium. However,the positive electrode active material layer 21B may further include anyone of, or two or more of other materials such as a positive electrodebinder and a positive electrode conductive agent. The positive electrodematerial is preferably a lithium-containing compound, and morespecifically, is preferably a lithium-containing composite oxide, alithium-containing phosphate compound, or the like.

The lithium-containing composite oxide is an oxide containing lithiumand one, or two or more other elements (elements other than lithium) asconstituent elements, and the oxide has, for example, any of a layeredrock salt-type crystal structure, a spinel-type crystal structure, andthe like. The lithium-containing phosphate compound is a phosphatecompound containing lithium and one, or two or more other elements asconstituent elements, and the compound has an olivine-type crystalstructure or the like.

The positive electrode binder includes any one of, or two or more ofsynthetic rubbers and polymer compounds, for example. The syntheticrubbers may be, for example, styrene-butadiene rubbers, fluorinerubbers, ethylene propylene diene, and the like. Examples of the polymercompounds include a polyvinylidene fluoride and a polyimide.

The positive electrode conductive agent includes, for example, any oneof, or two or more of carbon materials and the like, for example. Thecarbon materials may be, for example, graphite, carbon black, acetyleneblack, Ketjen black, and the like. The positive electrode conductiveagent may be, however, a metal material, a conductive polymer, or thelike as long as the agent is a conductive material.

The surface of the negative electrode foil 22A is preferably roughened.This is because the adhesion of the negative electrode active materiallayer 22B to the negative electrode foil 22A is improved due to aso-called anchor effect. In this case, the surface of the negativeelectrode foil 22A has only to be roughened at least in a region opposedto the negative electrode active material layer 22B. The rougheningmethod is, for example, a method such as forming fine particles throughthe use of electrolytic treatment. The electrolytic treatment providesthe surface of the negative electrode foil 22A with irregularities,because fine particles are formed on the surface of the negativeelectrode foil 22A with an electrolytic method in an electrolytic cell.Copper foil prepared by an electrolytic method is generally referred toas electrolytic copper foil.

The negative electrode active material layer 22B includes, as a negativeelectrode active material, any one of, or two or more of negativeelectrode materials capable of occluding and releasing lithium. Thenegative electrode active material layer 22B may, however, furtherinclude any one of, or two or more of other materials such as a negativebinder and a negative electrode conductive agent.

The negative electrode material is, for example, a carbon material. Thisis because a high energy density can be stably achieved due to the verysmall change in crystal structure at the time of occlusion and releaseof lithium. In addition, this is because the carbon materials alsofunction as negative electrode conductive agents, thus improving theconductivity of the negative electrode active material layer 22B.

The carbon materials may be, for example, graphitizable carbon,non-graphitizable carbon, and graphite. However, the interplanar spacingof the (002) plane in the non-graphitizable carbon is preferably 0.37 nmor more, and the interplanar spacing of the (002) plane in the graphiteis preferably 0.34 nm or less. More specifically, the carbon materialsmay be, for example, pyrolytic carbons, coke, glassy carbon fibers,fired products of organic polymer compounds, activated carbon, andcarbon blacks. Examples of the coke include pitch coke, needle coke, andpetroleum coke. The fired products of organic polymer compounds areobtained by firing (carbonizing) polymer compounds such as a phenolresin and a furan resin at appropriate temperatures. Besides, the carbonmaterials may be low-crystallinity carbon subjected to a heat treatmentat a temperature of about 1000° C. or lower, or may be amorphous carbon.It is to be noted that the shapes of the carbon materials may be any offibrous, spherical, granular and scaly.

In the lithium ion battery 1, when the open-circuit voltage (that is,the battery voltage) in a fully charged case is 4.25 V or higher, therelease amount of lithium per unit mass is increased also with the useof the same positive electrode active material as compared with a casewhere the open-circuit voltage in the fully charged case is 4.20 V, andthe amount of the positive electrode active material and the amount ofthe negative electrode active material are thus adjusted accordingly.Thus, a high energy density is achieved.

The separator 23 is interposed between the positive electrode 21 and thenegative electrode 22 to allow passage of lithium ions while preventinga short circuit due to the current caused by the contact between thepositive electrode 21 and the negative electrode 22. The separator 23 isany one of, or two or more of porous membranes such as synthetic resinsand ceramics, for example, and may be a laminated film of two or moreporous membranes. The synthetic resins may be, for example,polytetrafluoroethylene, polypropylene, polyethylene, and the like.

In particular, the separator 23 may include, for example, theabove-mentioned porous film (substrate layer), and a polymer compoundlayer provided on one or both sides of the substrate layer. This isbecause the adhesion of the separator 23 to each of the positiveelectrode 21 and the negative electrode 22 is improved, thus keeping theelectrode wound body 20 from warping. Thus, the inhibited decompositionreaction of the electrolytic solution, and also, the suppressed leakageof the electrolytic solution with which the substrate layer impregnated,make the resistance less likely to increase also with repeatedcharging/discharging, and keep the secondary battery from swelling.

The polymer compound layer contains, for example, a polymer compoundsuch as a polyvinylidene fluoride. This is because the homopolymer orthe copolymer is excellent in physical strength and electrochemicallystable. The polymer compound may be, however, a compound other than apolyvinylidene fluoride. In the case of forming the polymer compoundlayer, for example, a solution in which a polymer compound is dissolvedin an organic solvent or the like is applied to the substrate layer, andthen the substrate layer is dried. It is to be noted that afterimmersing the substrate layer in the solution, the base material layermay be dried. This polymer compound layer may include any one of, or twoor more of insulating particles such as inorganic particles, forexample. The type of the inorganic particles is, for example, analuminum oxide, an aluminum nitride, or the like.

The electrolytic solution includes a solvent and an electrolyte salt.The electrolytic solution may further include, however, any one of, ortwo or more of other materials such as additives.

The solvent includes any one of, or two or more of nonaqueous solventssuch as organic solvents. The electrolytic solution including anonaqueous solvent is a so-called nonaqueous electrolytic solution.

The nonaqueous solvent is, for example, a cyclic carbonate, a chaincarbonate, a lactone, a chain carboxylate, a nitrile (mononitrile), orthe like.

The electrolyte salt includes any one of, or two or more of salts suchas lithium salts, for example. However, the electrolyte salt may containa salt other than lithium salts, for example. The salt other thanlithium may be, for example, salts of light metals other than lithium.

The lithium salt may be, for example, lithium hexafluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate(LiClO₄), lithium hexafluoroarsenate (LiAsF₆), lithium tetraphenylborate(LiB(C₆H₅)₄), lithium methanesulfonate (LiCH₃SO₃), lithiumtrifluoromethanesulfonate (LiCF₃SO₃), lithium tetrachloroaluminate(LiAlCl₄), dilithium hexafluorosilicate (Li₂SF₆), lithium chloride(LiCl) and Lithium bromide (LiBr), and the like.

Above all, any one of, or two or more of lithium hexafluorophosphate,lithium tetrafluoroborate, lithium perchlorate, and lithiumhexafluoroarsenate is preferred, and lithium hexafluorophosphate is morepreferred.

The content of the electrolyte salt is not particularly limited, butpreferably 0.3 mol/kg to 3 mol/kg with respect to the solvent.

A method for manufacturing the lithium ion battery 1 according to oneembodiment will be described with reference to FIG. 4A to FIG. 4F.First, a positive electrode active material was applied to the surfaceof the band-shaped positive electrode foil 21A to form a covered partfor the positive electrode 21, and a negative electrode active materialwas applied to the surface of the band-shaped negative electrode foil22A to form a covered part for the negative electrode 22. In this case,the active material non-covered parts 21C and 22C without the positiveelectrode active material or negative electrode active material appliedwere prepared at one end of the positive electrode 21 in the widthwisedirection and one end of the negative electrode 22 in the widthwisedirection. Notches were formed in parts of the active materialnon-covered parts 21C and 22C, corresponding to the winding starts atthe time of winding. The positive electrode 21 and the negativeelectrode 22 were subjected to steps such as drying. Then, theelectrodes were stacked with the separator 23 interposed therebetweensuch that the active material non-covered part 21C of the positiveelectrode and the active material non-covered part 22C of the negativeelectrode were oriented in opposite directions, and spirally wound so asto form the through hole 26 in the central axis and dispose the formednotches near the central axis, thereby preparing the electrode woundbody 20 as shown in FIG. 4A.

Next, as shown in FIG. 4B, an end of a thin flat plate (for example, 0.5mm in thickness) or the like was pressed perpendicularly to the ends 41and 42 to locally bend the ends 41 and 42 and then prepare the grooves43 and 44. In accordance with this method, the groove 43 passing throughthe central axis and the grooves 44 not passing through the central axiswere prepared in radiation directions from the through hole 26. Thenumber and arrangement of the grooves 43 passing through the centralaxis and the grooves 44 not passing through the central axis, shown inFIG. 4B, are considered by way of example only. Then, as shown in FIG.4C, the same pressure was applied simultaneously from both electrodesides in a direction substantially perpendicular to the ends 41 and 42to bend the active material non-covered part 21C of the positiveelectrode and the active material non-covered part 22C of the negativeelectrode, and then form the ends 41 and 42 so as to have flat surfaces.In this case, the pressure was applied such that the active materialnon-covered parts at the ends 41 and 42 overlapped and then bent towardthe through hole 26. Thereafter, the fan-shaped part 31 of positiveelectrode current collecting plate 24 was subjected to laser welding tothe end 41, and the fan-shaped part 33 of the negative electrode currentcollecting plate 25 was subjected to laser welding to the end 42.

Thereafter, as shown in FIG. 4D, the band-shaped parts 32 and 34 of thecurrent collecting plates 24, 25 were bent, and the insulating plates 12and 13 (or insulating tapes) were attached to the positive electrodecurrent collecting plate 24 and the negative electrode currentcollecting plate 25, the electrode wound body 20 assembled as mentionedabove was inserted into the exterior can 11 shown in FIG. 4E, and thebottom of the exterior can 11 was subjected to welding. After injectingan electrolytic solution into the exterior can 11, sealing was performedwith the gasket 15 and the battery cover 14 as shown in FIG. 4F.

EXAMPLES

The present disclosure will be specifically described with reference toexamples of comparing the difference in internal resistance with the useof the lithium ion battery 1 prepared in the manner mentioned above. Itis to be noted that the present disclosure is not to be consideredlimited to the examples described below.

Examples 1 to 4

The numbers of the grooves 43 and 44 were changed, and the difference ininternal resistance was determined. For each of the end 41 of thepositive electrode and the end 42 of the negative electrode, N1 and N2were set respectively to 3 to 6 and 3 to 6, with N1 and N2 respectivelyrepresenting the number of the grooves 43 passing through the centralaxis and the number of the grooves 44 not passing through the centralaxis. The two types of grooves 43 and 44 were arranged in asubstantially equiangular manner. The width of the positive electrodeactive material layer 21B was adjusted to 59.0 (mm), and the width ofthe positive electrode 21 including the active material non-covered part21C was adjusted to 66.0 (mm). The width of the negative electrodeactive material layer 22B was adjusted to 62.0 (mm), and the width ofthe negative electrode 22 including the active material non-covered part22C was adjusted to 66.0 (mm). The width of the separator 23 wasadjusted to 64.0 (mm). The material of the positive electrode currentcollecting plate 24 was an Al alloy, and the material of the negativeelectrode current collecting plate 25 was a Cu alloy. The battery was21700 (diameter: 21 (mm), length: 70 (mm)) in size. The ends 41 and 42without the grooves 43 or 44 were subjected to laser welding to thepositive electrode current collecting plate 24 or the negative electrodecurrent collecting plate 25. L, D, and F (see FIG. 12A) were adjusted asshown in Table 1. The thickness of the positive electrode currentcollecting plate was adjusted to 0.2 (mm), the thickness of the positiveelectrode foil was adjusted to 0.01 (mm), the thickness of the negativeelectrode current collecting plate was adjusted to 0.08 (mm), and thethickness of the negative electrode foil was adjusted to 0.01 (mm).

Comparative Examples 1 to 5

The comparative examples were provided in the same manner as in Examples1 to 4, except that for each of the positive electrode 21 and thenegative electrode 22, N1 was set to 3 to 8, N2 was set to 0 or 9, thegrooves 43 not passing through the central axis were arranged in asubstantially equiangular manner, and L, D, and F (see FIG. 12A) wereadjusted as shown in Table 1.

The batteries described above were evaluated. Of the ends 41 and 42, thearea of a region overlapping the positive electrode current collectingplate 24 or the negative electrode current collecting plate 25 andincluding no grooves 43 or 44 or wrinkles or voids was defined as aweldable area. The number of spots where laser welding was actuallysuccessful was defined as the actual number of welded points. Theinternal resistance (direct-current resistance) of the battery wasmeasured, and the batteries with an internal resistance of 10.5 (mΩ) orless was determined as OK, whereas the other batteries were determinedas NG. The results are shown below.

TABLE 1 Positive Electrode Negative Electrode Number (N1) ThicknessThickness of Support (mm) of Actual (mm) of Grooves Number (N2) PositiveThickness Numbers Negative from Outer of Support Electrode (mm) of ofWelded Electrode Edge to Grooves Weldable Current Positive PointsCurrent Central at Outer Area L D F Collecting Electrode (AverageCollecting Axis Edge (mm²) (mm) (mm) (mm) Plate Foil Value) PlateExample 1 4 4 197.3 3.2 5 2.64 0.2 0.01 70 4 Example 2 3 3 206.3 3.2 54.67 0.2 0.01 78 3 Example 3 3 6 201.3 5 3.2 4.67 0.2 0.01 80 3 Example4 6 6 181.6 3 5.2 1.13 0.2 0.01 62 6 Comparative 4 0 175.2 — — 2.64 0.20.01 46 4 Example 1 Comparative 8 0 187.2 — — 0.6 0.2 0.01 36 8 Example2 Comparative 3 0 176.7 — — 4.67 0.2 0.01 48 3 Example 3 Comparative 6 0181.6 — — 1.13 0.2 0.01 50 6 Example 4 Comparative 3 9 181.3 6.2 2 4.670.2 0.01 50 3 Example 5 Negative Electrode Thickness (mm) of ActualThickness Negative Thickness Numbers (mm) of Electrode (mm) of of WeldedInternal Negative Weldable Current Negative Points Resistance ElectrodeArea L D F Collecting Electrode (Average (mΩ) of Foil (mm²) (mm) (mm)(mm) Plate Foil Value) Battery Determination Example 1 4 197.3 3.2 52.64 0.08 0.01 70 10.21 OK Example 2 3 206.3 3.2 5 4.67 0.08 0.01 7810.09 OK Example 3 6 201.3 5 3.2 4.67 0.08 0.01 80 10.01 OK Example 4 6181.6 3 5.2 1.13 0.08 0.01 62 10.42 OK Comparative 0 175.2 — — 2.64 0.080.01 46 14.98 NG Example 1 Comparative 0 187.2 — — 0.6 0.08 0.01 3615.29 NG Example 2 Comparative 0 176.7 — — 4.67 0.08 0.01 48 15.31 NGExample 3 Comparative 0 181.6 — — 1.13 0.08 0.01 50 12.22 NG Example 4Comparative 9 181.3 6.2 2 4.67 0.08 0.01 50 12.09 NG Example 5

The internal resistances of the examples were relatively low values of10.5 (mΩ) or less (determination: OK), whereas the internal resistancesof the comparative examples were relatively high values of about 12 to15 (mΩ) (determination: NG). The weldable areas of the examples areabout 10% to 20% larger than those of the comparative examples, and theactual numbers of welded points according to the examples are abouttwice larger than those of the comparative examples. FIG. 5 to FIG. 11show examples of views of the ends 41 and 42 viewed from the Z-axisdirection in FIG. 1. FIG. 5A and FIG. 5B correspond to Example 1, andFIG. 6A and FIG. 6B correspond to Example 2. FIG. 7A and FIG. 7Bcorrespond to Comparative Example 1, FIG. 8A and FIG. 8B correspond toComparative Example 2, FIG. 9A and FIG. 9B correspond to ComparativeExample 3, FIG. 10A and FIG. 10B correspond to Comparative Example 4,and FIG. 11A and FIG. 11B correspond to Comparative Example 5.

FIG. 5A to FIG. 11A (A in each of FIG. 5 to FIG. 11) are views of theends 41 and 42 after forming the grooves 43 and 44 and bending with aplate surface of a flat plate or the like (corresponding to FIG. 4Cbefore placing the current collecting plates), and blank regions wherestraight lines and polygonal lines are interrupted represent portionswith wrinkles or voids 51 formed by bending the ends 41 and 42 due tothe shortage of the grooves 43 and 44. FIG. 5B to 11B (B in each of FIG.5 to FIG. 11) are views after attaching the current collecting plates 24and 25 respectively to the surfaces of ends 41 and 42 in FIG. 5A to FIG.11A (A in each of FIG. 5 to FIG. 11) by laser welding. In FIG. 5B toFIG. 11B in common, a black circle indicates a site 52 where the ends 41and 42 and the current collecting plates 24 and 25 successfullyrespectively welded in electrical contact with each other, and a whitecircle indicates a site 53 where the ends 41 and 42 and the currentcollecting plates 24 and 25 respectively out of electrical contact witheach other due to a failure to be welded because of the wrinkles orvoids 51 at the ends 41 and 42 in spite of an attempt to be welded.

Referring to FIG. 5B to FIG. 11B, it is determined that the ends 41 and42 have flat surfaces, with relatively many welded sites also near thecentral axis in Examples 1 and 2 (FIG. 5A, FIG. 5B, FIG. 6A, and FIG.6B). It is determined that in Comparative Examples 1, 3, and 4 (FIG. 7A,FIG. 7B, FIG. 9A, FIG. 9B, FIG. 10A, and FIG. 10B), with theinsufficient numbers of grooves 43 passing through the central axis andof grooves 44 not passing through the central axis, wrinkles and voids51 formed at the ends 41 and 42, thus resulting fewer welded sites. Itis determined that Comparative Example 2 (FIG. 8A and FIG. 8B) has nowrinkles or voids 51 formed because of the sufficient number of grooves43 passing through the central axis, but has fewer sites successfullywelded, because of fewer weldable sites near the central axis of theelectrode wound body 20. It is determined that Comparative Example 5(FIG. 11A and FIG. 11B) has an excessively large number of grooves 44not passing through the central axis, and thus fewer sites that weldableto the electrode wound body 20. Due to these reasons, the internalresistances of the batteries according to the examples were lower thanthose of comparative examples. From the results in Table 1, in the caseof N1 being 3 or more and 6 or less and N2 being equal to or more thanN1 and equal to or less than 2×N1, the reduction in internal resistancewas successfully achieved.

Examples 11 to 14

The lengths of the grooves 44 not passing through the central axis atthe ends 41 and 42 were changed, and the difference in internalresistance was determined. The diameter of the through hole 26 wasadjusted to 4.2 (mm), and the diameters of the ends 41 and 42 wereadjusted to 20.4 (mm). As illustrated in FIG. 12A, the distance from anintersection V between the a segment UU′ and the groove 44 not passingthrough the central axis to the outer edges 27 and 28 along the groove44 not passing through the central axis was referred to as F (mm), withU representing the intersection between the groove 43 passing throughthe central axis and the outer edges 27 and 28, and U′ representinganother intersection between the groove 43 passing through the centralaxis and the outer edges 27 and 28, adjacent to the intersection U onthe outer edges 27 and 28. The length of the groove 44 not passingthrough the central axis was referred as L (mm). In this case, thelinear distance from the inner peripheral tip of the groove 44 notpassing through the central axis to the peripheral edge of the throughhole 26 was referred to as D (mm), and the distance (sum of L and D)from the outer edges 27 and 28 to the through hole 26 was referred to as8.1 (mm). The number (N1) of grooves 43 passing through the central axiswas adjusted to 3 to 6, L was set so as to meet L≥1.1×F, and D was setso as to meet D≥1.5 (mm). The number (N2) of grooves 44 not passingthrough the central axis was adjusted to be the same as the number (N1)of grooves 43 passing through the central axis, and the groove 43 andgroove 44 were alternately arranged in a substantially equiangularmanner. FIG. 12A corresponds to Example 11, FIG. 12B corresponds toExample 12, FIG. 12C corresponds to Example 13, and FIG. 12D correspondsto Example 14. In each of FIGS. 12A to 12D, one groove 44 not passingthrough the central axis is shown for avoiding complexity. In FIG. 12Bto FIG. 12D, the positional relationship among L, F, and D is notillustrated, but is the same as that in FIG. 12A. The thickness of thepositive electrode current collecting plate was adjusted to 0.2 (mm),the thickness of the positive electrode foil was adjusted to 0.01 (mm),the thickness of the negative electrode current collecting plate wasadjusted to 0.08 (mm), and the thickness of the negative electrode foilwas adjusted to 0.01 (mm). The thickness of the positive electrode foil,the thickness of the negative electrode foil, the thickness of thepositive electrode current collecting plate, and the thickness of thenegative electrode current collecting plate were measured with the useof a micrometer (MDC-25 MX from Mitutoyo Corporation). The thickness ofthe positive electrode foil means the thickness of one foil at a site ofthe positive electrode active material non-covered part without anyinsulating layer. The thickness of the negative electrode foil means thethickness of one foil at the negative electrode active materialnon-covered part.

Comparative Examples 11 to 12

The comparative examples were provided in the same manner as in Examples11 to 14, except that the value of N1 was adjusted to 3, L was set so asto meet L<1.1×F in Comparative Example 11, and D was set so as to meetD<1.5 (mm) in Comparative Example 12.

The batteries described above were evaluated. The internal resistance(direct-current resistance) of the battery was measured, and thebatteries with an internal resistance of 10.5 (mΩ) or less wasdetermined as OK, whereas the other batteries were determined as NG. Theresults are shown below.

TABLE 2 Number (N1) of Support Positive Electrode Negative electrodeGrooves Thickness Thickness from Outer (mm) of Thickness (mm) ofThickness Internal Edge to Current (mm) of Current (mm) of ResistanceCentral 1.1 × F L D Collecting Current Collecting Current (mΩ) of Axis F(mm) (mm) (mm) (mm) Plate Collector Plate Collector BatteryDetermination Example 11 3 5.25 5.775 5.8 2.3 0.2 0.01 0.08 0.01 10.22OK Example 12 4 3.08 3.388 3.5 4.6 0.2 0.01 0.08 0.01 10.17 OK Example13 5 2.01 2.211 2.4 5.7 0.2 0.01 0.08 0.01 10.28 OK Example 14 6 1.411.551 1.7 6.4 0.2 0.01 0.08 0.01 10.11 OK Comparative 3 5.25 5.775 5.03.1 0.2 0.01 0.08 0.01 14.92 NG Example 11 Comparative 3 5.25 5.775 6.81.3 0.2 0.01 0.08 0.01 15.41 NG Example 12

From the results of Examples 11 to 14, the resistance value was equal toor less than 10.5 (mΩ) as the criterion for determination(determination: OK) in the case of L≥1.1×F and D≥1.5 (mm), whereas fromthe results of Comparative Examples 11 and 12, the resistance value washigher than 10.5 (mΩ) as the criterion for determination (determination:NG) in the case of L<1.1×F or D<1.5 (mm). Accordingly, from the resultsin Table 2, the reduction in internal resistance was successfullyachieved in the case of L≥1.1×F and D≥1.5 (mm).

Examples 21 to 25

The thickness of the positive electrode current collecting plate and thethickness of the positive electrode foil were changed, and thedifference in internal resistance was then determined. The ratio(TC1/TC) was adjusted to 5 or more and 40 or less, with TC1 representingthe thickness of the positive electrode current collecting plate and TCrepresenting the thickness of the positive electrode foil, and the ratio(TA1/TA) was adjusted to 20, with TA1 representing the thickness of thenegative electrode current collecting plate and TA representing thethickness of the negative electrode foil. The number (N1) of groovespassing through the central axis and the number (N2) of grooves notpassing through the central axis were each adjusted to 4, L was adjustedto 3.5 (mm), D was adjusted to 4.6 (mm), and F was adjusted to 3.08(mm).

Examples 26 to 30

The thickness of the negative electrode current collecting plate and thethickness of the negative electrode foil were changed, and thedifference in internal resistance was then determined. The ratio(TA1/TA) was adjusted to 5 or more and 40 or less, and the ratio(TC1/TC) was adjusted to 20. N1, N2, L, D, and F were adjusted in thesame manner as in Examples 21 to 25.

Comparative Examples 21 to 24

The thickness of the positive electrode current collecting plate and thethickness of the positive electrode foil were changed, or the thicknessof the negative electrode current collecting plate and the thickness ofthe negative electrode foil were changed, and the difference in internalresistance was then determined. The ratio (TC1/TC) or the ratio (TA1/TA)was adjusted to a value smaller than 5 or a value larger than 40. N1,N2, L, D, and F were adjusted in the same manner as in Examples 21 to25.

The batteries described above were evaluated. The internal resistance(direct-current resistance) of the battery was measured, and thebatteries with an internal resistance of 10.5 (mΩ) or less wasdetermined as OK, whereas the other batteries were determined as NG. Theresults are shown below. After the laser welding, visual observationdetermined the number of holes in the foil or the current collectingplate was defined as the number of defective perforated welding.

TABLE 3 Positive Electrode Negative Electrode Thickness Thickness (mm)of (mm) of Positive Thickness Negative Thickness Electrode (mm) ofElectrode (mm) of Current Positive Current Negative Collecting ElectrodeL D F Collecting Electrode Plate Foil Ratio N1 N2 (mm) (mm) (mm) PlateFoil Example 21 0.200 0.010 20 4 4 3.5 4.6 3.08 0.200 0.010 Example 220.300 0.010 30 4 4 3.5 4.6 3.08 0.200 0.010 Example 23 0.100 0.020 5 4 43.5 4.6 3.08 0.200 0.010 Example 24 0.100 0.010 10 4 4 3.5 4.6 3.080.200 0.010 Example 25 0.200 0.005 40 4 4 3.5 4.6 3.08 0.200 0.010Example 26 0.200 0.010 20 4 4 3.5 4.6 3.08 0.050 0.010 Example 27 0.2000.010 20 4 4 3.5 4.6 3.08 0.080 0.010 Example 28 0.200 0.010 20 4 4 3.54.6 3.08 0.100 0.010 Example 29 0.200 0.010 20 4 4 3.5 4.6 3.08 0.2000.010 Example 30 0.200 0.010 20 4 4 3.5 4.6 3.08 0.400 0.010 Comparative0.300 0.080 4 4 4 3.5 4.6 3.08 0.200 0.010 Example 21 Comparative 0.3000.007 43 4 4 3.5 4.6 3.08 0.200 0.010 Example 22 Comparative 0.200 0.01020 4 4 3.5 4.6 3.08 0.300 0.070 Example 23 Comparative 0.200 0.010 20 44 3.5 4.6 3.08 0.250 0.006 Example 24 Defective Internal NegativeElectrode Perforated Resistance L D F Welding (mΩ) of Ratio N1 N2 (mm)(mm) (mm) (number) Battery Determination Example 21 20 4 4 3.5 4.6 3.080 10.11 OK Example 22 20 4 4 3.5 4.6 3.08 0 10.08 OK Example 23 20 4 43.5 4.6 3.08 0 10.06 OK Example 24 20 4 4 3.5 4.6 3.08 0 10.00 OKExample 25 20 4 4 3.5 4.6 3.08 0 10.39 OK Example 26 5 4 4 3.5 4.6 3.080 10.28 OK Example 27 8 4 4 3.5 4.6 3.08 0 9.96 OK Example 28 10 4 4 3.54.6 3.08 0 10.17 OK Example 29 20 4 4 3.5 4.6 3.08 0 10.21 OK Example 3040 4 4 3.5 4.6 3.08 0 10.18 OK Comparative 20 4 4 3.5 4.6 3.08 15 15.25NG Example 21 Comparative 20 4 4 3.5 4.6 3.08 31 16.11 NG Example 22Comparative 4 4 4 3.5 4.6 3.08 20 14.98 NG Example 23 Comparative 42 4 43.5 4.6 3.08 29 15.82 NG Example 24

In Examples 21 to 30, the internal resistance was equal to or less than10.5 (mΩ) as the criterion value for determination (determination: OK),and in Comparative Examples 21 to 24, the internal resistance was avalue larger than 10.5 (mΩ) (determination: NG). In Comparative Examples21 to 24, the internal resistance was increased, because a hole wasformed in the foil or the current collecting plate due to the heat ofwelding at the time of welding, thereby causing a site to be defectivelywelded. Accordingly, from the results in Table 3, the reduction ininternal resistance was successfully achieved in the case of the ratio(TC1/TC) being 5 or more and 40 or less, or the ratio (TA1/TA) being 5or more and 40 or less.

While the embodiment of the present disclosure have been concretelydescribed above, the contents of the present disclosure are not to beconsidered limited to the embodiment described above, and it is possibleto make various modifications based on technical idea of the presentdisclosure.

Although the grooves include the groove 43 passing through the centralaxis and the groove 44 not passing through the central axis, any groovemay be employed, and grooves in forms other than the grooves 43 and 44may be present. The grooves 43 and 44 are formed in the radiationdirections from the central axis, but may be formed in other directions.

The positive electrode current collecting plate 24 and the negativeelectrode current collecting plate 25 respectively include thefan-shaped parts 31 and 33 in the shape a fan, which may have othershapes.

FIG. 13 is a block diagram illustrating a circuit configuration examplein the case of applying a battery according to an embodiment of thepresent disclosure (hereinafter, referred to appropriately as asecondary battery) to a battery pack 330. The battery pack 300 includesan assembled battery 301, an exterior, a switch unit 304 including acharge control switch 302 a and a discharge control switch 303 a, acurrent detection resistor 307, a temperature detection element 308, anda control unit (controller) 310.

In addition, the battery pack 300 includes a positive electrode terminal321 and a negative electrode terminal 322, and in the case of charging,the positive electrode terminal 321 and the negative electrode terminal322 are connected respectively to a positive electrode terminal and anegative electrode terminal of a charger to perform charging. Inaddition in the case of using an electronic device, the positiveelectrode terminal 321 and the negative electrode terminal 322 areconnected respectively to a positive electrode terminal and a negativeelectrode terminal of the electronic device to perform discharging.

The assembled battery 301 has a plurality of secondary batteries 301 aconnected in series and/or in parallel. The secondary battery 301 a is asecondary battery according to the present disclosure. It is to be notedthat FIG. 13 shows therein a case where six secondary batteries 301 aare connected to arrange two batteries in parallel and three batteriesin series (2P3S) as an example, but any other connecting method may beemployed, such as n in parallel and m in series (n and m are integers).

The switch unit 304 includes the charge control switch 302 a and a diode302 b as well as the discharge control switch 303 a and a diode 303 b,and the switch unit 304 is controlled by the control unit 310. The diode302 b has a polarity in the reverse direction with respect to thecharging current flowing in the direction from the positive electrodeterminal 321 to the assembled battery 301 and in the forward directionwith respect to the discharging current flowing in the direction fromthe negative electrode terminal 322 to the assembled battery 301. Thediode 303 b has a polarity in the forward direction with respect to thecharging current and in the reverse direction with respect to thedischarging current. It is to be noted that the switch unit 304 isprovided on the positive side in the example, but may be provided on thenegative side.

The charge control switch 302 a is turned off if the battery voltagereaches an overcharge detection voltage, and is controlled by acharge/discharge control unit such that no charging current flowsthrough the current path of the assembled battery 301. After the chargecontrol switch 302 a is turned off, only discharging is possible throughthe diode 302 b. In addition, the charge control switch 302 a is turnedoff if a large current flows at the time of charging, and is controlledby the control unit 310 so as to cut off a charging current flowingthrough the current path of the assembled battery 301. The control unit(controller) 310 includes at least one of a central processing unit(CPU), a processor or the like.

The discharge control switch 303 a is turned off if the battery voltagereaches an overdischarge detection voltage, and is controlled by thecontrol unit 310 such that no discharging current flows through thecurrent path of the assembled battery 301. After the discharge controlswitch 303 a is turned off, only charging is possible through the diode303 b. In addition, the discharge control switch 303 a is turned off ifa large current flows at the time of discharging, and is controlled bythe control unit 310 so as to cut off a discharging current flowingthrough the current path of the assembled battery 301.

The temperature detection element 308 is, for example, a thermistor, isprovided in the vicinity of the assembled battery 301 to measure thetemperature of the assembled battery 301 and supplies the measuredtemperature to the control unit 310. The voltage detection unit 311measures the voltages of the assembled battery 301 and of the secondarybatteries 301 a constituting the assembled battery, performs A/Dconversion of the measured voltages, and supplies the converted voltagesto the control unit 310. A current measurement unit 313 measures acurrent with the use of the current detection resistor 307, and suppliesthe measured current to the control unit 310.

The switch control unit 314 controls the charge control switch 302 a anddischarge control switch 303 a of the switch unit 304, based on thevoltages and current input from the voltage detection unit 311 and thecurrent measurement unit 313. When the voltage of any of the secondarybatteries 301 a becomes equal to or lower than the overcharge detectionvoltage or the overdischarge detection voltage, or when a large currentflows rapidly, the switch control unit 314 transmits a control signal tothe switch unit 304 to prevent overcharge, overdischarge, andovercurrent charge and discharge.

In this regard, for example, in the case where the secondary battery isa lithium ion secondary battery, the overcharge detection voltage isdetermined to be, for example, 4.20 V±0.05 V, and the overdischargedetection voltage is determined to be, for example, 2.4 V±0.1 V.

For the charge/discharge switch, for example, a semiconductor switchsuch as a MOSFET can be used. In this case, the parasitic diode of theMOSFET functions as the diodes 302 b and 303 b. In the case where aP-channel FET is used as the charge/discharge switch, the switch controlunit 314 supplies control signals DO and CO respectively to therespective gates of the charge control switch 302 a and dischargecontrol switch 303 a. In the case of the P-channel type, the chargecontrol switch 302 a and the discharge control switch 303 a are turnedon by a gate potential that is lower than the source potential by apredetermined value or more. More specifically, in normal charging anddischarging operations, the control signals CO and DO are set to a lowlevel to turn on the charge control switch 302 a and the dischargecontrol switch 303 a.

Then, for example, in overcharge or overdischarge, the control signalsCO and DO are set to a high level to turn off the charge control switch302 a and the discharge control switch 303 a.

A memory 317 includes a RAM and a ROM, and includes, for example, anEPROM(Erasable Programmable Read Only Memory) that is a nonvolatilememory. In the memory 317, the numerical value calculated by the controlunit 310, the internal resistance value of the battery in the initialstate for each secondary battery 301 a, measured at the stage of themanufacturing process, and the like are stored in advance, and can bealso appropriately rewritten. In addition, the full charge capacity ofthe secondary battery 301 a is stored therein, thereby allowing, forexample, the remaining capacity to be calculated together with thecontrol unit 310.

A temperature detection unit 318 measures a temperature with the use ofthe temperature detection element 308, performs charge/discharge controlat the time of abnormal heat generation, and performs a correction inthe calculation of the remaining capacity.

The above-described battery according to an embodiment of the presentdisclosure can be mounted on or used to supply electric power to, forexample, electronic devices and electric vehicles, electric aircrafts,and devices such as electric storage devices.

Examples of the electronic devices include lap-top computers,smartphones, tablet terminals, PDAs (personal digital assistants),mobile phones, wearable terminals, cordless phone handsets, videomovies, digital still cameras, electronic books, electronicdictionaries, music players, radios, headphones, game machines,navigation systems, memory cards, pacemakers, hearing aids, electrictools, electric shavers, refrigerators, air conditioners, televisions,stereos, water heaters, microwave ovens, dishwashers, washing machines,dryers, lighting devices, toys, medical devices, robots, roadconditioners, and traffic lights.

Furthermore, examples of the electric vehicles include railway vehicles,golf carts, electric carts, and electric automobiles (including hybridautomobiles), and the battery is used as a driving power supply or anauxiliary power supply for the electric vehicles. Examples of theelectric storage devices include power supplies for power storage forbuildings such as houses or power generation facilities.

Among the above-described application examples, a specific example of anelectric storage system in which an electric storage device with theabove-described battery according to the present disclosure applied isused will be described below.

An example of an electric tool, for example, an electric driver to whichthe present disclosure can be applied will be schematically describedwith reference to FIG. 14. The electric driver 431 has a motor 433 suchas a DC motor housed in a main body. The rotation of the motor 433 istransmitted to a shaft 434, and the shaft 434 drives a screw into atarget object. The electric driver 431 is provided with a trigger switch432 operated by a user.

A battery pack 430 and a motor control unit (motor controller) 435 arehoused in a lower housing of a handle of the electric driver 431. As thebattery pack 430, the battery pack 300 can be used. The motor controlunit (motor controller) 435 controls the motor 433. Each unit of theelectric driver 431 other than the motor 433 may be controlled by themotor control unit 435. Although not shown, the battery pack 430 and theelectric driver 431 are engaged by engagement members providedrespectively. As described later, each of the battery pack 430 and themotor control unit (motor controller) 435 includes at least one of amicrocomputer, a central processing unit (CPU), a processor or the like.Battery power is supplied from the battery pack 430 to the motor controlunit 435, and information on the battery pack 430 is communicatedbetween the microcomputers.

The battery pack 430 is, for example, detachable from the electricdriver 431. The battery pack 430 may be built in the electric driver431. The battery pack 430 is attached to a charging device at the timeof charging. It is to be noted that when the battery pack 430 isattached to the electric driver 431, a part of the battery pack 430 maybe exposed to the outside of the electric driver 431 to allow the userto visibly recognize the exposed part. For example, the exposed part ofthe battery pack 430 may be provided with an LED to allow the user tocheck light emission and non-light emission of the LED.

The motor control unit 435 controls, for example, the rotation/stop androtation direction of the motor 433. Furthermore, power supply to theload is cut off at the time of overdischarge. For example, the triggerswitch 432 is inserted between the motor 433 and the motor control unit435, and when the user pushes the trigger switch 432, power is suppliedto the motor 433 to rotate the motor 433. When the user returns thetrigger switch 432, the rotation of the motor 433 is stopped.

An example in which the present disclosure is applied to a power supplyfor an electric aircraft will be described with reference to FIG. 15.The present disclosure can be applied to a power supply of an unmannedaircraft (so-called drone). FIG. 15 is a plan view of an unmannedaircraft. The airframe includes a cylindrical or rectangular tube bodyas a central part, and support shafts 442 a to 442 f fixed to an upperpart of the body. As an example, the body has a hexagonal tubular shape,and the six support shafts 442 a to 442 f are adapted to extend radiallyin an equiangular manner from the center of the body. The body and thesupport shafts 442 a to 442 f are made of a lightweight andhigh-strength material.

Motors 443 a to 443 f as driving sources for rotor blades are attachedrespectively to tips of the support shafts 442 a to 442 f. Rotor blades444 a to 444 f are attached to the rotation shafts of the motors 443 ato 443 f. A circuit unit 445 including a motor control circuit (motorcontroller) for controlling each motor is attached to the central part(the upper part of the body portion) where the support shafts 442 a to442 f intersect. The motor control circuit (motor controller) includesat least one of a central processing unit (CPU), a processor or thelike.

Furthermore, a battery unit as a power source is disposed at a positionbelow the body. The battery unit includes three battery packs so as tosupply electric power the pair of a motor and a rotor blade that have anopposing interval of 180 degrees. Each battery pack includes, forexample, a lithium ion secondary battery and a battery control circuitthat controls charging and discharging. The battery pack 300 can be usedas the battery pack. The motor 443 a and the rotor blade 444 a form apair with the motor 443 d and the rotor blade 444 d. Similarly, (motor443 b and rotor blade 444 b) form a pair with (motor 443 e and rotorblade 444 e), and (motor 443 c and rotor blade 444 c) form a pair with(motor 443 f and rotor blade 444 f). These pairs are equal in number tothe battery packs.

An example of applying the present disclosure to an electric storagesystem for an electric vehicle will be described with reference to FIG.16. FIG. 16 schematically illustrates an example of the configuration ofa hybrid vehicle that adopts a series hybrid system to which the presentdisclosure is applied. The series hybrid system is intended for avehicle that runs on an electric power-driving force conversion device,with the use of electric power generated by a generator driven by anengine, or the electric power stored once in the battery.

The hybrid vehicle 600 carries an engine 601, a generator 602, theelectric power-driving force conversion device 603, a driving wheel 604a, a driving wheel 604 b, a wheel 605 a, a wheel 605 b, a battery 608, avehicle control device 609, various sensors 610, and a charging port611. The above-described battery pack 300 according to the presentdisclosure is applied to the battery 608.

The hybrid vehicle 600 travels with the electric power-driving forceconversion device 603 as a power source. An example of the electricpower-driving force conversion device 603 is a motor. The electricpower-driving force conversion device (converter) 603 is operated by theelectric power of the battery 608, and the torque of the electricpower-driving force conversion device 603 is transmitted to the drivingwheels 604 a and 604 b. It is to be noted that the electricpower-driving force conversion device 603 can be applied to both analternate-current motor and a direct-current motor by using directcurrent-alternate current (DC-AC) or reverse conversion (AC-DCconversion) in a required location. The various sensors 610 control theengine rotation speed via the vehicle control device (vehiclecontroller) 609, and control the position (throttle position) of athrottle valve, not shown. The various sensors 610 include a speedsensor, an acceleration sensor, an engine rotation speed sensor, and thelike. the vehicle control device (vehicle controller) 609 includes atleast one of a central processing unit (CPU), a processor or the like.

The torque of the engine 601 is transmitted to the generator 602, andthe torque makes it possible to reserve, in the battery 608, theelectric power generated by the generator 602.

When the hybrid vehicle 600 is decelerated by a braking mechanism, notshown, the resistance force during the deceleration is applied as torqueto the electric power-driving force conversion device 603, and theregenerative electric power generated by the electric power-drivingforce conversion device 603 is reserved in the battery 608 by thetorque.

The battery 608 is connected to a power source outside the hybridvehicle 600, thereby making it also possible to receive electric powersupply from the external power supply with the charging port 611 as aninput port, and then reserve the received power.

Although not shown, the vehicle may be provided with an informationprocessing device that performs information processing related tovehicle control, based on information on the secondary battery. Examplesof such an information processing device include, for example, aninformation processing device that displays the remaining battery level,based on information on the remaining level of the battery.

It is to be noted that as an example, the series hybrid vehicle has beendescribed above, which runs on the motor with the use of the electricpower generated by the generator driven by the engine, or the electricpower stored once in the battery. However, the present disclosure can bealso effectively applied to parallel hybrid vehicles which use theoutputs of both an engine and a motor as a driving source, andappropriately switch three systems of running on only the engine,running on only the motor, and running on the engine and the motor.Furthermore, the present disclosure can be also effectively applied toso-called electric vehicles that run on driving by only a driving motorwithout using any engine.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A secondary battery comprising: an electrode wound body that has apositive electrode and a negative electrode stacked with a separatorinterposed therebetween and has a wound structure; and a positiveelectrode current collecting plate and a negative electrode currentcollecting plate, the electrode wound body and the positive electrodecurrent collecting plate and the negative electrode current collectingplate accommodated in an exterior can, wherein the positive electrodeincludes a first covered part covered with a positive electrode activematerial layer and a positive electrode active material non-covered parton a positive electrode foil, the negative electrode includes a secondcovered part covered with a negative electrode active material layer anda negative electrode active material non-covered part on a negativeelectrode foil, the positive electrode active material non-covered partis joined to the positive electrode current collecting plate at a firstend of the electrode wound body, the negative electrode active materialnon-covered part is joined to the negative electrode current collectingplate at a second end of the electrode wound body, one or both of thepositive electrode active material non-covered part and the negativeelectrode active material non-covered part have a flat surface formed bybending toward a central axis of the wound structure and overlappingeach other, the flat surface has a first groove passing through thecentral axis and a second groove not passing through the central axis,and a part of the flat surface without any groove passing through thecentral axis or groove not passing through the central axis is bonded toat least one of the positive electrode current collecting plate or thenegative electrode current collecting plate.
 2. The secondary batteryaccording to claim 1, wherein N1 meets 3≤N1≤6, and wherein N1 representsa number of grooves passing through the central axis, and wherein N1 andN2 meet N1≤N2≤2× N1, and wherein N2 represents a number of grooves notpassing through the central axis.
 3. The secondary battery according toclaim 1, wherein L, F, and D meet L≥1.1× F and D≥1.5 (mm), and wherein Frepresents a distance from an intersection V between a line segment UU′and a groove not passing through the central axis to an outer edge ofthe flat surface along the groove not passing through the central axis,and U represents an intersection between a groove passing through thecentral axis and the outer edge, and U′ represents an intersectionbetween another groove passing through the central axis and the outeredge, and L represents a length of the groove not passing through thecentral axis, and D represents a distance from an inner peripheral tipof the groove not passing through the central axis to a peripheral edgeof a closest through hole.
 4. The secondary battery according to claim1, wherein a ratio of a thickness of the positive electrode currentcollecting plate to a thickness of the positive electrode foil meets5≤TC1/TC≤40, wherein TC1 represents the thickness of the positiveelectrode current collecting plate, and TC represents the thickness ofthe positive electrode foil.
 5. The secondary battery according to claim1, wherein a ratio of a thickness of the negative electrode currentcollecting plate to a thickness of the negative electrode foil meets5≤TA1/TA≤40, wherein TA1 represents the thickness of the negativeelectrode current collecting plate, and TA represents the thickness ofthe negative electrode foil.
 6. The secondary battery according to claim1, wherein a material of the positive electrode current collecting plateincludes aluminum or an aluminum alloy.
 7. The secondary batteryaccording to claim 1, wherein a material of the negative electrodecurrent collecting plate includes a simple substance of nickel, a nickelalloy, copper, a copper alloy, or a composite thereof.
 8. The secondarybattery according to claim 1, wherein a width of the positive electrodeactive material non-covered part is larger than a width of the negativeelectrode active material non-covered part, an end of the positiveelectrode active material non-covered part and an end of the negativeelectrode active material non-covered part is protruded outward from theseparator, and a length of a part of the positive electrode activematerial non-covered part protruded from one end of the separator in awidth direction is larger than a length of a part of the negativeelectrode active material non-covered part protruded from the other endof the separator in the width direction.
 9. The secondary batteryaccording to claim 1, wherein a part of the positive electrode activematerial non-covered part that faces the negative electrode with theseparator interposed therebetween has an insulating layer.
 10. Thesecondary battery according to claim 1, wherein an open end of theexterior can is sealed by a sealing plate, and the sealing plate servesas an external terminal.
 11. The secondary battery according to claim 1,wherein a part of the flat surface without any groove passing throughthe central axis or groove not passing through the central axis isjoined by welding to at least one of the positive electrode currentcollecting plate or the negative electrode current collecting plate. 12.A battery pack comprising: the secondary battery according to claim 1; acontroller configured to control the secondary battery; and an exteriorbody that encloses the secondary battery.
 13. An electronic devicecomprising the secondary battery according to claim
 1. 14. An electronicdevice comprising the battery pack according to claim
 12. 15. Anelectric tool comprising the battery pack according to claim 12, whereinthe electric tool is configured to use the battery pack as a powersupply.
 16. An electric aircraft comprising: the battery pack accordingto claim 12; a plurality of rotor blades; a motor that rotates each ofthe rotor blades; a support shaft that supports each of the rotor bladesand the motor; a motor controller configured to control rotation of themotor; and a power supply line that supplies power to the motor, whereinthe battery pack is connected to the power supply line.
 17. The electricaircraft according to claim 15, comprising: a plurality of pairs of therotor blades facing each other; and a plurality of the battery packs,wherein the plurality of pairs of rotor blades and the plurality ofbattery packs are equal in number.
 18. An electric vehicle comprising:the secondary battery according to claim 1; a conversion device thatreceives power supply from the secondary battery to convert the power toa driving force for the electric vehicle; and a controller configured toperform information processing related to vehicle control, based oninformation on the battery.